Engine modelling and sounds?

[JimmiG 244]

A bit late to the party, but I just bought the PA46T yesterday. After having flown the RA Turbine Duke extensively, I've really started to like turboprops and wanted a single-engine variant too.

 

While the PA46T lacks any detailed documentation, much of what's in the Flying Guide for the Duke seems to apply, with a few differences. I realize that they're two totally different airplanes, so there should be differences, but there are a few things that stand out.

 

In the Duke, when you reduce propeller RPM, the pitch and volume of the sound decreases, making for a quieter cabin. In the PA46T, reducing propeller RPM increases the engine sound. I thought the point of reducing prop RPM is to make the engine run smoother and quieter? With both models, Torque increases with decreased prop RPM, which is supposedly correct according to the flying guide.

 

With the PA46T, torque seems to decrease significantly at higher altitudes, where as with the Duke, it can be maxed out even at FL280. It's still possible to max out ITT and Gas Gen % at high altitudes.

 

Any opinions on these differences and whether they are caused by differences between the actual airplanes and engines, or by different approaches to engine modelling within FSX/P3D by the respective developers? I have the Cumulative SP and the optional patch installed.

 

Really enjoying the plane so far. I feared it would kill my frame-rate since cockpit is mostly glass, but surprisingly, there's almost no FPS hit compared to e.g. the steam gauge HD C337.

[andy1975 13]

Hi,

 

the biggest differences are in the engines, the Pa46T uses PT6A-21 whereas the Turbine Duke got the - 35 installed. I do not know the "envelope" of each engines, but the -35 ´s have more power-reserve in many aspects than the -21 ´s , which are also used in the Carenado King Air C90B btw...

 

Carenado modeled the Piper Malibu Jetprop DL , which has the -21´s , if you look at the Jetprop-Homepage, they also converse a more powerfull DLX - variant which does HAVE the -35´s just like the Turbine Duke. Take a look at their homepage, there you can find some comparisons regarding their power.

 

Regarding the engine noise related to the Prop-RPMs I guess it is related to the subjective imagination of the sound creator or actual passenger. A lower prop-pitch (from 2400rpm to about 1900rpm) will give you a more comfortable sound-enviroment with its sound-frequency, but as far as I know it will not be quieter in db ...

 

Cheers!

[JimmiG 244]

Carenado modeled the Piper Malibu Jetprop DL , which has the -21´s , if you look at the Jetprop-Homepage, they also converse a more powerfull DLX - variant which does HAVE the -35´s just like the Turbine Duke. Take a look at their homepage, there you can find some comparisons regarding their power.

 

I think this explains why I wasn't getting quite the cruise speed I was expecting (250+ kts). Bit of a shame that they didn't model the more powerful version, but I guess it's being modeled after a specific PA46T that Carenado had access to which makes it authentic at least.

 

Regarding the engine noise related to the Prop-RPMs I guess it is related to the subjective imagination of the sound creator or actual passenger. A lower prop-pitch (from 2400rpm to about 1900rpm) will give you a more comfortable sound-enviroment with its sound-frequency, but as far as I know it will not be quieter in db ...

 

The strange thing is that the frequency also increases with reduced RPM. The frequency/pitch of the engine sound seems to be directly related to the Torque rather than propeller RPM, and since Torque increases when you reduce RPM, the pitch of the sound increases as well.

[HawkDsl 50]

There are very few planes I dont change the sound on in some way. I have the King Air TSS HD sound set, and used the engine sounds from it for this plane (and the Duke too for that matter). Carenado has great jet whine on this bird, but the prop sounds are hideous.

[HawkDsl 50]

Back to the OP on the PT6

 

 

Wanting a modern Meridian, at least in performance, I changed my "aircraft.cfg" settings to the Meridian specs (or I should say, real darn close)

 

---

performance="Maximum Speed\t\n270 kts            310 mph\t498 kmh\n\nCruise Speed\t\n270 kts            310 mph \t498 kmh\n\nEngine\t\n Pratt & Whitney     550 shp\n\nPropeller\t\nFour-bladed Hartzell\n\nMaximum Range\t\n1410 nm          1,623 sm \t2,611 km\n\nService Ceiling\t\n27,000 ft         8,230 m\n\nFuel Capacity\t\n154 U.S. gal        483 L \n\nEmpty Weight\t\n2,970 lb \t          1,347 kg\n\nMaximum Gross Weight\t\n4,318 lb \t          1,959 kg\n\nUseful Load\t\n1,348 lb  \t          611 kg\n\nLength\t\n30.08 ft\t          9.17 m\n\nWingspan\t\n43.00 ft\t           13.11 m\n\nHeight\t\n11.25 ft\t           3.43 m\n\nSeating\t\nUp to 6"

 

 

[GeneralEngineData]

 

engine_type = 5                                 

Engine.0 = 10.0, 0.0, -0.3                      

fuel_flow_scalar   =  1.10                     

min_throttle_limit = -0.35                      

              

 

[TurbineEngineData]

 

fuel_flow_gain       = 0.03                

inlet_area              = 0.5                   

rated_N2_rpm       = 37500                

static_thrust          = 165                  

 

[turboprop_engine]

 

power_scalar            = 1.165                 

maximum_torque      = 1315  

 

You should mod the G500 for 188 kts red line, 180 top speed, up the gear to 169 kts to deploy without damage, prop max rpm to

2000, but is not necessary. These setting are in the G500_cfg.XML file inside the "G500_P46T.cab" in the FSX/gauges folder.

[JimmiG 244]

Well, I'm getting more used to the aircraft and engine. I think it mostly comes down to my inexperience with turbine engines vs piston.

Using the fuel flow .cfg tweak and the correct JetPROP DL performance charts, I'm getting very accurate performance and fuel flows.

 

When setting cruise power, I've found it easier to rely on prop RPM and fuel flow, rather than prop RPM and torque. Once I've decided on a cruise RPM setting (usually 2000 or 2100 RPM), I then adjust the throttle to get the appropriate fuel flow, for example around 28-29gph at 24,000 ft for 230kts TAS.